CAIRO
— Investigators still don't know who carried out last Thursday's attacks in London. But they say those responsible were probably Islamist terrorists who viewed their assault as revenge for Britain's part in the Iraq war.

The attacks that killed at least 52 in London follow two years in which the Iraq war has inflamed Islamist hatred of the US and key allies like Britain.

According to US assessments, the turmoil in Iraq has replaced the still-simmering conflict in Afghanistan as the chief recruiter of international jihadis. Analysts say anger over the conflict is helping to spread the ideology of global jihad to young Muslims in Europe.

But it is the confluence of America's decision to invade Iraq and new communication technologies that has created the most powerful machine for recruiting new terrorists in history, says Evan Kohlmann, an American terrorism consultant who has tracked jihadi websites since the late 1990s.

America and its allies are now facing a multifront war: In Iraq, which is turning out a new generation of Arab jihadis; in Europe, where Muslim admirers of Al Qaeda are embracing the cause because of anger over the Iraq war; and on the Internet, which has become a megaphone for radical jihadi ideologies.

Counterterrorism officials often talk about the phenomenon of "terrorist dispersal," which is when radicalized foreigners carry jihad and their guerrilla skills back to their homelands.

But most analysts speculate that those responsible for Thursday's attacks in London were not veterans of the Iraqi insurgency. Instead, the best guess is that they were composed primarily of Muslims living in Europe, inspired by Al Qaeda sympathizers who promise salvation and glory in exchange for violence, much as was the case with the Madrid blasts that killed 190 last year.

"The world is just starting to understand the real influence of the Internet as an open university of jihad,'' says Reuven Paz, the head of the Project for the Research of Islamic Movements in Israel. "Like the attacks in Madrid, the bombings in London should be viewed as an export of the war in Iraq to Europe, based on local adherents of global jihad rather than on volunteers from the heart of the Arab world."

In the 1980s, the war against the Soviets in Afghanistan, with its thousands of Arab fighters financed by the US and others, also served as a potent rallying point for would-be martyrs. Not only was Al Qaeda - "the base" in Arabic - created from among these fighters, but clandestine videos of brave Mujahideen attacks were spread around the world.

Today, videos and messages of support for Islamist fighters spread much faster. Insurgent in "martyrdom operations" appear on websites within days of attacks in Iraq, and the latest calls to carry jihad to Western capitals from the likes of Ayman al-Zawahiri, Osama bin Laden's No. 2 and Al Qaeda's chief ideologue, spread around the globe within minutes.

"Whatever framework we use to talk about Iraq - take Afghanistan for instance - it's whatever happened there, but on steroids,'' says Toby Craig Jones, a political scientist and analyst of events in Saudi Arabia for the International Crisis Group, a Brussels-based think tank. "It seems to be proceeding much more quickly this time."

To be sure, the vast majority of Muslims are as horrified by such attacks as anyone else, and a growing number of Muslim scholars are speaking out against the methods and motives the global jihadis. But Islamist terrorism has never been a widespread phenomenon. "If we're talking about percentages, maybe the supporters of global jihad are only 1 percent of the Muslim world,'' says Paz.

A Saudi ideologue who goes by the handle "Lewis Attiyatullah" online and with whom Paz held an e-mail correspondence with until Lewis apparently went underground, spelled out what Al Qaeda and its ideological allies see as the benefits of the US presence in Iraq in an open letter to Tony Blair first published in April 2004.

In his letter, Lewis said he expects that fighting in Iraq will create "a resistance that would develop into a culture of jihad," and that attacks must be made on Western capitals like London that have supported the war in Iraq. He also expresses pleasure about how Iraq, in his view, is inducting new members into the global jihad. "I wish you could listen to what the returnees from Iraq say. Fighting the enemy became their greatest pleasure ... this notion became like a virus for them."

Within Iraq, a small percentage of the insurgency is composed of foreign fighters. The US military in Iraq estimates that there are around 1,000 members of an insurgency that many others say numbers at least 15,000. But foreign fighters are far more likely to be suicide bombers than Iraqi fighters, a reflection of the extreme religious convictions that underpin their involvement.

Paz calculated in a March 2005 paper that of around 200 documented suicide bombers in Iraq, 61 percent were Saudi. In an assessment running through June by Mr. Kohlmann, of 300 foreigners reported killed in Iraq, 165 were Saudi, 38 were Syrian, 16 Kuwaiti, and 14 Jordanian. Kohlmann says nine Muslims from Europe have also been reported killed in Iraq, one of them from Britain.

Both men expect that foreigners who survive the fighting in Iraq are likely to carry the fight back to homelands like Saudi Arabia, a close US ally whose monarchy is frequently attacked on Islamist websites as corrupt. The foreigners in Iraq, based on "martyrdom wills" and websites linked to Abu Musab al-Zarqawi, the Jordanian militant who has been declared the head of Al Qaeda in Iraq, appear to have few qualms about even killing other Muslims.

Paz says the frequency with which jihadis in Iraq are willing to justify the killings of civilians and Muslims is a sharp departure from the previous generation weaned on Afghanistan, which was brutal to be sure, but generally had stricter limits on what were seen as legitimate targets. "The Iraqi alumni are going to be more dangerous than the Afghan alumni. They have no limits, no red lines," he says.